1. Field of the Invention
The present invention relates to an improvement of a solid state color image pick-up apparatus provided with minute color filters in front of the light receiving face thereof to pick-up color images.
2. Description of Prior Arts
Solid-state pick-up device made as a CCD, BBD, MOS device or hybrid devices thereof, which has a novel characteristic which is not possessed by the conventional picture pick-up tubes is making rapid development. The solid state apparatus, on top of smallness and light weight, low power consumption, high reliability and long life, has advantages of having no burning by image on photoelectric face and no distortion of image pattern. Accordingly, the device recently comes into wide uses in remote monitoring, application in a distance measuring, or in color television cameras using three chips, two chips or single chip. Besides, the solid state apparatus does not make distortion of pattern due to environmental magnetic field and electric field, and hence is possible to make precise measurement of position and length. In making a two-chip or single chip type color image pick-up camera, filter is bonded in front of the chip to produce separate color signals thereby; in such case, the positions of the respective colors of filter are obtained by electric means, since there is no pattern distortion like the case of conventional pick-up tube utilizing electromagnetic deflections; and therefore, the separation of color signal is possible without a particular index signal or a particular processing of signal.
It is known that, in order to make a color image pick-up camera with a single chip, a filter 12 having an array of color filter elements to correspond to picture elements of a solid state device 11 is bonded in front of the solid state device, as shown in FIG. 1, which schematically shows only a small fraction of the picture elements and corresponding filters, wherein C.sub.11, C.sub.12, C.sub.13 . . . , C.sub.11 ', C.sub.12 ', C.sub.13 ' . . . , C.sub.21, C.sub.22, C.sub.23 . . . C.sub.21 ', C.sub.22 ' . . . C.sub.44 . . . designate filter elements of the filter 12 to be disposed in front of the picture elements A.sub.11, A.sub.12, A.sub.13 . . . , A.sub.11 ', A.sub.12 ', A.sub.13 ' . . . , A.sub.21, A.sub.22, A.sub.23 . . . , A.sub.21 ', A.sub.22 ' . . . , respectively of the solid state device. A color image pick-up camera is constituted in a manner that signal of the above-mentioned solid state device are then sampled or detected thereby to separate luminance signal component and chrominance signal component therefrom. In the filter 12, the filter elements of the rows C.sub.11, C.sub.12, C.sub.13 . . . , C.sub.21, C.sub.22, C.sub.23 . . . are for the first field of the interlaced scanning video picture and the filter elements of the rows C.sub.11 ', C.sub.12 ', C.sub.13 ' . . . and C.sub.21 ', C.sub.22 ', C.sub.23 ' . . . are for the second field of the interlaced scanning video picture.
In the conventional color image pick-up camera of the above-mentioned constitution, the element color filters C.sub.11, C.sub.12, C.sub.13, C.sub.11 ', C.sub.12 ', C.sub.13 ' . . . , C.sub.44 ' have been constituted principally with primary colors, for example, red, blue and green, and therefore efficiency of light utility has been poor. This is because, for example, the green filter elements substantially cut off other component of light, namely red component and blue component, and so on. Generally speaking, from the view point of the light utility efficiency, transparent filters are highest, a complementary color filters next and primary color filters last.
Another prior art is described in the U.S. patent application Ser. No. 235,428 (corresponding to European Patent Application No. 81101089.1 first published unexamined on Aug. 26, 1981 under the publication number 0034361), gist of an exemplary embodiment of which is shown in FIG. 2, wherein in a horizontal row nH, (n+1)H, . . . are for the first field and the horizontal row nH', (n+1)H', . . . are for the second field. For each field, a horizontal row having filter elements of W-Cy-W-Cy . . . (wherein W means transparent and Cy means cyanic) and another horizontal row having filter elements of Ye-W-Ye-W . . . (wherein Ye means yellow) are alternately disposed from the top to the bottom. Since this apparatus is constructed with transparent (W) elements and complementary color (Cy & Ye) elements, the light utilization efficiency is high, and therefore, high sensitivity solid state image senser is obtainable. However, the conventional apparatus of FIG. 2 has a problem that resolving power is different between in the horizontal direction and in the vertical direction of the picture. That is, in the apparatus the vertical resolving power is only 50% of the horizontal resolving power. This is because in the vertical direction, two cyanic filter elements as well as two yellow filter elements are disposed in vertical sequence for height of two picture elements or two horizontal rows, while in the horizontal direction are cyanic elements as well as one yellow filter elements is disposed alternately with one transparent filter element.